Three Downer staff worked to clear the graffiti using waterblasters yesterday after they were alerted by another Downer employee in Palmerston.
A New Zealand Post worker, who would not be identified, said the people putting the graffiti on buildings and letterboxes were "complete morons".
Waitaki District Councillor for the Waihemo ward Jan Wheeler said camera surveillance might be needed in Palmerston to deter people from causing damage.
She had discussed the need for surveillance cameras in Palmerston with Waitaki District Council staff.
The placement of surveillance cameras in Palmerston would need to be discussed with Palmerston residents and with the Waihemo Community Board, Mrs Wheeler said.
Senior Constable Stefan Witehira, of Palmerston, was investigating the graffiti attack.